There are many areas where it is desirable to provide an inexpensive, temporary barrier layer between a substrate and the atmosphere. Such a barrier layer might serve to protect the atmosphere from deleterious materials which would escape from the substrate, such as odors and blowing trash from landfills, dust or noxious fumes from spills, and the like. Such a barrier layer might also be used to protect a substrate from adverse conditions in the atmosphere, as in protecting growing fruit, vegetables and plants from unseasonal frost.
In landfill operations for example, it has been suggested to replace the daily compacted earth cover with a hardenable plastic foam. This is the subject of U.S. Pat. Nos. 4,421,788 and 4,519,338. The foam employed according to these patents is prepared using a foaming agent and a liquid synthetic resin, such as a precondensate of urea and formaldehyde.
One principal advantage of using foam instead of the conventional dirt cover resides in the elimination of the expense of placing and compacting the earth which require significant labor and heavy equipment. Another advantage is the elimination of multiple, daily, layers of earth fill which occupy significant volume of the landfill.